It's a fun game. I had a great time playing it. I liked a lot how the hostages were found on paths that seemed just alternative routes. The exploration is really enjoyable. The spikes fall felt really good to nail on first try. And the final boss was also fun. It took me a while to realise what I was supposed to hit to actually hurt the machine, but once I found out, it felt good being able to finish it quickly, applying all the power ups to navigate around the stage.
Very impressive work, I would definitely play a longer version.
If I may contribute with something, I read a good idea from comments, that is "stunning the enemies instead of destroying them", but then i'd twist the alert mode:
To get away from alert mode would have to hide in a bush or phase out of enemy sight for enough time (the counter only starts when hidden/phased). And after alert mode is gone, any remaining enemy go away, as now they wouldn't have anything else to chase.
This would enable strategies like luring enemies to one side of the screen, stunning then rushing to the other side where there is a bush or timing the end of stun with start of phasing to get enough "out of sight" time and disable alert.
Thanks for sharing this cool game with all of us. Congratulations on your work!